These substitutes can replace 1 cup of sour cream
1 cup (225 grams) plain yogurt
3/4 cup (180 ml) sour milk, buttermilk or plain yogurt + 1/3 cup (75 grams) melted butter
1 tablespoon lemon juice or vinegar plus enough whole milk to fill 1 cup (240 ml) (let stand 5-10 minutes)
Hope that helps.